BioMedical Admissions Test (BMAT) Practice Test 2026 - Free BMAT Practice Questions and Study Guide

When Fe3+ ions are added to a NaOH solution, a precipitate of iron(III) hydroxide (Fe(OH)3) is formed. This precipitate is characterized by its brown color, which arises from the nature of iron(III) ions and their interactions in solution. Iron(III) hydroxide appears as a rust-colored solid due to the hydroxide ions reacting with the Fe3+ ions to form the insoluble compound.

The presence of brown in the color spectrum is significant because other options suggest different compounds or states that do not match the reaction involving Fe3+ and NaOH. A white precipitate would typically indicate the formation of substances such as aluminum or zinc hydroxides that do not correlate with iron chemistry. Colorless would imply solvation without precipitation indicating soluble compounds, while yellow could suggest other iron species such as iron(II) or certain complex ions not formed in this reaction with NaOH. Hence, the brown precipitate is the definitive outcome of adding Fe3+ to NaOH, reflecting the characteristic chemistry of iron in this context.